Wiki info about Bf 109 E-3

The Messerschmitt Bf 109 was a single-seat monoplane fighter used by the Luftwaffe before and during WWII. It was used as a fighter, interceptor, high-altitude interceptor, fighter-bomber and reconnaissance aircraft.
The Bf 109 E variant, or "Emil", was in fact the first truly mass-produced variant of the venerable Messerschmitt Bf 109 family. Powered by a new Daimler-Benz DB 601A direct fuel injection engine, the Emil also had a redesigned supercharger. However, most importantly, the engine proved much more reliable than its predecessors. First production variants reached front-line units in early 1939. The Emil was armed with two 7.9mm machine guns in the engine housing and two 20mm cannon in the wings.